Squirrels and martens

By Tim Felce (Airwolfhound) (Squirrel  Uploaded by russavia) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
By Tim Felce (Airwolfhound) (Squirrel Uploaded by russavia) [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
When I walk through St James’s Park, as I sometimes do, I am always (and it is always) struck by the number of people smiling at Grey Squirrels, photographing Grey Squirrels and feeding Grey Squirrels.  These people, many of whom are ‘foreign’, from their accents at least, would be shocked to hear this lovely, friendly, cute mammal called a ‘tree rat’ (although they probably would say that there is not that much wrong with rats either).

But there is little or no doubt that the spread of the Grey Squirrel has pushed our native Red Squirrel back into the celtic fringe of the UK through a combination of disease transmission and competition. And so, cute as they are, I look somewhat askance at Grey Squirrels as I pass by them, although you can’t help but smile at them, can you?

By Ray eye (Photograph by Ray eye) [CC BY-SA 2.0 de (http://creativecommons.org/licenses/by-sa/2.0/de/deed.en)], via Wikimedia Commons
By Ray eye (Photograph by Ray eye) [CC BY-SA 2.0 de (http://creativecommons.org/licenses/by-sa/2.0/de/deed.en)], via Wikimedia Commons
It was, of course, the land owning class which introduced this cute but controversial mammal into our shores, and it is now the descendants 0f those landowners, and some foresters, who moan most about their continued existence in this country.  There are various slightly crack-brained schemes around which are supposed to help Red Squirrels, and some that probably will, but there is now an approach that seems to offer more hope than  the ‘get your gun out’ approach does.

Grey Squirrels were introduced into the UK from North America in the nineteenth century long after the main predator of squirrels had been extirpated from much of the UK. That species, was, and is, the Pine Marten. Perhaps, just perhaps, the Grey Squirrel has done so well because it has arrived in a predator-free zone?

There is now some evidence for  this idea, quite good evidence which has been around for a while, although I missed it a couple of years ago (I suspect because I was working hard for WWF at the time).  In the couple of days I spent with Forest Enterprise staff a couple of weeks ago, I sat through a presentation by Emma Sheehy. Her study in Ireland, where Grey Squirrels arrived only relatively recently but then romped westwards across the country reprising their impact on the Red Squirrel in Ireland as they had in Britain, showed that the increase in numbers and range of the Pine Marten seemed to be pushing Grey Squirrels back towards the Irish Sea and allowing Red Squirrels to regain their range too.

sylvia duckworth [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
sylvia duckworth [CC BY-SA 2.0 (http://creativecommons.org/licenses/by-sa/2.0)], via Wikimedia Commons
Pine Martens eat squirrels, red ones and grey ones, although of course, Red Squirrels evolved in a world full of Pine Martens whereas Grey Squirrels did not. In fact, interestingly (very interestingly), Grey Squirrels do not overlap in range with the marten species that might eat them in North America.

Grey Squirrels are bigger than Reds and therefore cannot escape Pine Marten attacks by seeking out the smallest branches of trees, and Greys spend more time on the ground than Reds and so are more vulnerable, perhaps, to Marten attacks.

The working hypothesis would be that if our landowners had not got rid of the Pine Marten then perhaps when they released the Grey Squirrel, it would not have been able to take such a hold on our woodlands (at the expense of our native Red Squirrel).  And therefore, the interesting proposition is that if you have a box full of Pine Martens and let them go in your local wood they might well get rid of the Greys by eating a few of them and creating a ‘landscape of fear’ which rather cramps the style of the rest of them. Very interesting.

Now I am not suggesting that you should get a box full of Pine Martens and start letting them go, but I can see why Forest Enterprise should be interested in this idea.  Of course, if we had a Forest and Wildlife Service then it would be a done deal!  All those publicly-owned forests and a remit that requires the body to enhance biodiversity, and it would be a no-brainer (after careful consideration and trials etc etc etc).

Pine Marten range. IUCN Red List of Threatened Species, species assessors and the authors of the spatial data. [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
Pine Marten range. IUCN Red List of Threatened Species, species assessors and the authors of the spatial data. [CC BY-SA 3.0 (http://creativecommons.org/licenses/by-sa/3.0)], via Wikimedia Commons
I suspect that the main objections to there being more Pine Martens will come from shooting estates worried about their (non-native, introduced) Pheasants. Can you imagine the conflicting feelings of the members of the Country Land and Business Association over whether they could have an easy cost-effective solution to the problems that Grey Squirrels cause forestry but only at the expense of a native predator being re-established in our artificial countryside? I think we should give it a go. It all sounds great fun and rather promising, and an interesting case study for the role of native predators in preventing non-native species becoming established.

I’d be a bit surprised if I ever see Red Squirrels being admired by tourists in St James’s Park as it is more difficult to imagine Pine Martens getting to grips with Greys in the middle of our largest cities, but, you never know!

And I suspect those Lynx will sort out a few of the Muntjac too.


Emma Sheehy is now studying these issues at the University of Aberdeen. She is appearing on Radio 4’s Costing the Earth this afternoon at 330pm. Other press coverage here, here and an article by Emma here. And a bit of her science here.

Photo: Thomas Avery
Photo: Thomas Avery


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23 Replies to “Squirrels and martens”

  1. The Eastern Gray Squirrels, as you have there, have also taken over here in California, pushing out our native Western Grays (fluffier, more shy and reclusive), especially in urban areas. Our back garden is home to a large oak tree, and is therefore a major attraction for a huge population of the Eastern Grays. At any given moment we can watch many of them scampering all over. I know they're non-native but you can't help but feel fond of them, can you?

  2. "...it is more difficult to imagine Pine Martens getting to grips with Greys in the middle of our largest cities"

    True, but the Pine Marten's close relative the Beech Marten (Martes foina) is commonly found in urban and sub-urban areas in Germany and France so you never know!

      1. I'd love it if it could be proved that the stone marten was once native, but I think doubtful. Apparently with stuffed pine martens the yellow fur on the throat whitens with age to look like their stone marten cousin's and that has raised suspicions that they once lived in Britain (love to know if there is any other potential evidence re this). Think unlikely they got to blighty before the channel became a very wide river then sea. But as it co-exists with the same species we have here over on the Calais side should not be an invasive species - so same situation re little owl, bitterling, midwife toad, wall lizard etc - what could be called near natives. A stone marten, wrongly identified as a pine marten, recently ran onto the pitch of a televised football game somewhere in Europe and nipped one of the players as he tried to grab it. I might start watching footie if that was a regular occurence.

  3. "in Ireland, where Grey Squirrels arrived only relatively recently"...

    Greys have actually been in Ireland a long time...more than a century (introduced in Co. Longford in1911, 35 years after the first UK introductions) and I remember them being common in parts of Sligo when I was a kid in the '60s. What's changed (I think) is Ireland. It's now unrecogniseable when I go back, with LOTS more trees in the landscape, both conifers and spindly spinneys of beech and sycamore together with lots of blackthorn. This has probably facilitated their spread in the last few years.

    The Pine Marten hypothesis is exciting because GS's are now well established at many sites in N. Italy amidst almost complete indifference / ignorance of the public as to the dangers and aided by idiot animal libbers (the head of the Italian equivalent of Natural England being prosecuted and found guilty of "mis-treatment of animals" when he approved a project to attempt to eliminate one of the first colonies on the grounds that baby grey squirrels starved to death when lactating females were trapped and euthanased). The main fear was that they would get away from the northern city parks and reach the river Ticino and use it as a corridor to reach the Alps, the huge hazelwoods used to produce Nutella ('Che disastro!') and little to stop them reaching Vladivostok in the long term across the northern boreal forests.
    That said, the spread has not been spectacular at all, suggesting something is holding it back. Could that be the massed ranks of Beech Martens (in the foothills, even in towns), Pine Martens (higher up in the Alps) as well as healthy populations of Goshawks just about everywhere in what are much more intact ecosystems than those in UK?

  4. It's a tough call. As a vegan I believe all animal life is sacred however I also would prefer to see our native red squirrel be firmly put back on the map. As we know greys destroy birds nesting and they can cause a lot of damage in gardens especially bulbs.
    I would welcome the return of the pine martin and i would definately love to see the return of the lynx, but i doubt that the greedy land owners wouldnt.
    I would be worried for the lynx of course as i reckon the shooting brigade would be out there taking a crack at it whether it was a protected species would make no difference to them

  5. This sounds promising Mark. The introduction of the grey squirrel is an ecological disaster. Hopefully more study will confirm that pine martins do definitely push back the grey squirrel. I also understand that goshawks will prey preferentially on grey squirrels so between the pine martin and the goshawk we might have a chance of putting back the balance of nature. As you say Mark, I am sure it will be the shooting estates that will oppose such a corrective course of action since it was they who have been responsible for the dimise of the goshawk and pine martin in the first place. With a few exceptions these estates have so much to answer for in the destruction and the inbalance of our wildlife.

  6. This demonstrates the strong ecological argument to reintroduce native mammals to their former range. As you mention, the reintroduction of pine marten should be a "no brainer", but unfortunately I can't see the majority of the landed classes and their gamekeepers reaching the same conclusion. Their preferred method will always be the trap and the gun.

    The Vincent Wildlife Trust has been working to increase the pine marten's range in the UK, while Lynx UK is hoping to trial Lynx reintroduction in Norfolk, Cumbria and Aberdeenshire. This is so positive, as it will help to restore some of our damaged ecosystems.

    I would like to see these two small organisations receive more support from our bigger conservation bodies (especially the RSPB now that it works for "nature" and not just birds) with lobbying/PR etc. It is essential that people can see the benefits of such reintroductions especially at the release sites, as they are bound to face a lot of opposition from the CLA, CA, NFU etc and probably DEFRA too. Although saying that, what happened with the Devon beavers does show that a lot of people want a "wilder" UK.

  7. Add in Goshawk and you have a great way of putting 'Red Alert' to bed!! 3 televised nests have included 95% in Derbyshire, 68% in Devon and a new 90% in the Midlands grey squirrels used for feeding their young.

  8. Sorry, I didn't make it particularly clear, but the NFU/DEFRA opposition is likely to come from the reintroduction of the lynx and not the pine marten!

    I guess Songbird Survival will be feeling pretty confused by this research since pine martens eat birds and eggs, in addition to grey squirrels.

  9. There have been several cases of 'marten bombers' in England; there are now at least a few animals established where I'm based in the New Forest, and foresters have been reporting a big decrease in the number of squirrels being bagged each year. The significant increase in the local goshawk population probably has a big part to play in this, but the influence of martens is another possibility to consider. Then of course there was the recent sighting of a marten near Bude in Cornwall, so at least some people certainly are depositing 'boxes of pine martens'! A more official translocation programme is being developed by Vincent wildlife trust this year however, with reintroduction into three sites in Wales hopefully taking place by as soon as 2016.

  10. Whilst I love the idea of a Forest and Wildlife service I think you are being a bit optimistic to think it could simply go ahead with Pine Martens regardless - you only have to look at NE and Hen Harriers to feel the force of establishment political pressure. Hopefully, though, Fe might get away with introducing Martens to places like the Forest of Dean where Greys are currently an intractable problem (due to the mixed age, mixed species and beautiful forest providing absolutely everything a Grey Squirrel needs !) As you know, FE has been a leader in restoring missing wildlife - fighting a long battle for beavers in Scotland.

  11. There was an attempt to reintroduce red squirrels into Regents Park in the 1980s, referred to in Gavin Weightman and Mike Birkhead's book 'City Safari: Wildlife in London' (a book of an LWT TV series of the same name which if you've not read it Mark might make an interesting alongside the Nature in Towns and Cities book you recently reviewed?). The reds were being radio tracked to see "how they got on with" the greys. I wonder what happened? Weightman and Birkhead suggest that the decline of the reds due to disease may have been happening anyway before the greys arrived and that they are vulnerable in the UK at the edge of their range. No idea of the veracity of this claim. They make similar observations to your good self about how the greys have endeared themselves to the public which makes "controlling" them very difficult and sensitive (LWT weren't allowed to film them being trapped and shot in the Royal parks apparently).

    One impact of greys Rackham talks about is the long term threat to hazel, due to their habit of eating hazel nuts when still green, meaning "a young hazel is now a rarity" though it's longevity may see it through a few centuries. So would a Pine Marten reintroduction help a much loved native tree? Interesting.

    Like others I can't help rather liking greys despite everything - and why not? It wasn't their fault they were introduced.

    1. '' One impact of greys Rackham talks about is the long term threat to hazel, ''

      ''..Scientific studies conducted by researchers from universities Wilkes, Princeton (Steele et al. 1996) and Purdue (Goheen & Swihart 2003) have shown that the unrivalled leaders in seed dispersion – and subsequently in forest regeneration – are grey squirrels (Sciurus carolinensis) .. ''


      PS. '' Using the methodology of researchers from Purdue University (Goheen & Swihart 2003), ICSRS conducted in 2015-2016 a similar experiment in three UK locations, from 9th December 2015 to 14th April 2016 (ICSRS 2016b). The results of this experiment were congruous with the findings of scientists from Purdue University (Goheen & Swihart 2003). It’s worth noting however that in the UK experiment (ICSRS 2016b) grey squirrels distributed seeds not only in broadleaved woodlands but also in coniferous forests where they also turned out to be the main natural forest regenerators (ICSRS 2016b)...''

  12. You might be interested in The Vincent Wildlife Trust's plans to re-establish pine martens in Wales and England, starting with the first translocations to mid Wales this autumn. See http://www.pine-marten-recovery-project.org.uk/

    1. Lizzie - I think the pine marten re-establishment project is very exciting and I'm fully supportive of it. I think I see the logic of starting in mid-Wales, but I have one concern (which may be totally unfounded). If pine martens have existed and still exist at a vey low level in this region, can you be confident that whatever factors have prevented the existing population from expanding 'under its own steam' will not act in the same way on the re-introduced animals?
      Apologies if I have not understood the situation properly!

      1. Alan- thanks for your support and that is a very reasonable concern. We are confident that the pine marten population in Wales has fallen so low as to become functionally extinct; there are simply not enough animals to constitute a viable breeding population. A boost in the number of pine martens through translocation will increase genetic diversity and hopefully allow the population to recover (similar to the situation with red kites in Wales). We are confident that there is sufficient evidence that the two causes of population decline- persecution and habitat loss- have been addressed. Pine martens are legally protected so persecution should be minimal and we have undertaken extensive work to select release sites in mid Wales that are biologically suitable for martens, in terms of habitat, prey availability and minimal conflict with human interests.

        1. Lizzie - many thanks for your informative reply. I hope you're right about persecution!
          Best of luck with the project.

  13. For years there have been comments from the field sports sector that red squirrels were being threatened by goshawks and pine martens. The fact that they had co-existed and in fact co-evolved for thousands of years seemed to be neither here nor there. I suppose a lot of people just accepted their statements as a fact. Fantastic that now a more natural system with more predators is becoming established (slowly) this is being shown up for the utter rubbish it was and always will be. It's really blown a hole in the image that gamekeepers present of themselves as countryside stewards upon whom our wildlife depends (a modest bunch aren't they?). Good fun to look around for previous statements from them re pine martens killing off red squirrels, now it's about red faces. Notice how there has been a noticeable silence from some quarters re this brilliant development?

    Do think that the fact we have such a knackered eco system in first place is big reason why invasives are such a problem. If there had been more wild boar on the ground rooting up soil and helping to prevent any plant species establishing a monoculture, but allowing a more varied selection to drop seed, invigorate rootstock may be Japanese knotweed and others wouldn't have got quite such a hold on big parts of the country, held back rhoddie too?. Robins love following them for worms and grubs as well, another excellent keystone species.

  14. The repeated blaming in the article and the comments of "landowners" for the loss of the pine marten and the presumption that they'd reject its return is unwarranted. The deforestation of most of the UK, which was at its worst in the early 20th century is surely most to blame for the loss of the marten, which unlike the grey didn't find a home in suburban gardens. The comment on the spread of the greys in Ireland being related to its reforestation is suggestive on this. A couple of owners of park land introduced greys, that's hardly the basis for demonising all of them, and the main objections to eradicating them now coms from urban and suburban non-landowners. Landowners come in all shapes and sizes, and as far as woodlands are concerned the state is the biggest. Most land doesn't host shoots, most shoots are on open farmland and use game cover to provide shelter, rather than in forests where the birds can't fly. Of course there can be conflict but a quick search suggests the main one has been where the (thriving) pine martens are imperilling in a small area of Scotland the recovery of the capercaillie population , which is not currently - and I suspect will never again be- a quarry species. There are some real trade-offs, it's a nonsense to pretend they don't exist. But gamekeepers happily shoot and trap grey squirrels which do predate on pheasant and partridge chicks, which reds don't. Pick your opponents for genuine reasons, not out of class prejudice.

  15. '' But there is little or no doubt that the spread of the Grey Squirrel has pushed our native Red Squirrel back into the celtic fringe of the UK through a combination of disease transmission and competition.''

    Pox (SQPV):
    Data collected by scientists about the places of the most frequent occurrence of SQPV between 2001-2012 in that area (White & Lurz 2014) overlap for the most part with data collected by us about the places where before the pox outbreak intensive supplementary feeding of red squirrels using shared feeders was introduced. Considering the fact that grey squirrels co-existed in the area with red squirrels for a few decades and never before – prior to the introduction of supplementary feeding using shared feeders – were there pox outbreaks noted like those that took place in recent years, it is more than likely that humans could have significantly promoted the spread of SQPV among squirrel population in the UK.


    The scientific research shows minimal competition for food and habitat between European red squirrel (Sciurus vulgaris) and grey squirrel (Sciurus carolinensis). The same research shows that significant variability of reproduction – observed in different years – which occurs naturally within red squirrel populations living in areas with no grey squirrels (Wauters & Lens 1995, Wauters et al. 2000, Gurnell et al. 2004) can also occur among red squirrels inhabiting the same area with grey squirrels (data from Wauters & Lens 1995, Wauters et al. 2000, Gurnell et al. 2004). It is also well known that small and fragmented habitats are very unfavourable for sustaining a red squirrel population (Verboom & van Apeldoorn 1990, Gurnell & Pepper 1991, Rodriguez & Andren 1999, Flaherty et al. 2012).

    It is also not a new discovery that red squirrel populations living in – big and of suitable tree species composition – coniferous forests are much less vulnerable to seasonal/annual variations in seeds availability (Wauters & Lens 1995). Also for many years it's been known which tree species – like Sitka spruce – have very negative effect on the state of red squirrel population living in such habitat (Verboom & van Apeldoorn 1990, Gurnell & Pepper 1991, Lurz et al. 1998) which has been confirmed by more recent studies and reports (Bryce et al. 2002, 2005, Huxley 2003, Harris et al. 2006, Bryant 2011, Haigh et al. 2015).


    Red squirrels mortality:
    Regardless whether the studies were conducted in big woodland areas with "low level of urbanisation" (Shuttleworth 2001) or they included areas "more urbanised" (Dutton 2004, Simpson et al. 2013) the main cause (even up to 94%) of unnatural deaths in red squirrel population in the UK was human activity.


  16. Ps. The most of tree species currently planted in the UK – mainly in commercial forests – are of little or no use for red squirrels conservation (Lurz et al. 1998, Ticknell 2000, Scottish Environment Statistics 2006, Harris et al. 2006) and at the same time support the growth of grey squirrel population (Bryce et al. 2002, Harris et al. 2006). Even though the planted woodland area in the UK keeps growing in the recent decades, the area of forests favourable for red squirrels relatively shrinks at a quick rate – plantations of trees favourable for red squirrels are now mature and intensely felled and at the same time replaced with less favourable but more profitable tree species (Lurz et al.1998, Ticknell 2000, Bryce et al. 2002, Scottish Environment Statistics 2006, Harris et al. 2006).



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